In the last two decades significant attention has been devoted to the physics of low dimensional semiconductor structures. Among those, semiconductor nanoparticles are of particular interest, due to the pronounced influence of the three-dimensional size confinement on their electronic and optical properties. Extensive effort has been devoted for the production of high quality semiconductor nanoparticles, motivated by their potential use in new and emerging technologies.
Currently, there are two main methods for the fabrication of semiconductor nanoparticles, namely epitaxial growth and colloidal chemistry techniques. Epitaxial growth of nanoparticles on top of a substrate with a different lattice constant leads to strain induced three-dimensional islands, known as Stranski Krastanow (SK) quantum dots.
The SK method produces relatively large dots, with weak quantum confinement, and with size fluctuation, neighboring islands coalescence, compositional in-homogeneity and unresolved physics preventing reproducible and uniform results. This method requires ultra high vacuum as well as other complex and expensive equipment. Furthermore, the liberty to choose the substrate is limited.
The colloidal method enables the reproducible but not continued formation of nanoparticles, with a variety of sizes and shapes, with initial distributions of 10<σ<20% in diameter, and with some control on surface properties, but it does not allow doping of the nanoparticles. Furthermore, the organic capping has a key role in any self-assembly created by these nanoparticles and prevents a highly packed structure and induces undesirable and hard to control surface properties due to the role of the ligands (namely, the organic molecules attached to the nanoparticle surface as a monolayer through covalent, dative or ionic bonds).